JP2021064600A - Tungsten-doped lithium manganese iron phosphate-based fine particle, powder material including the same, and production method of powder material - Google Patents

Abstract

To provide tungsten doped lithium manganese iron phosphate-based fine particles which enable the production of a superior lithium ion battery.SOLUTION: A tungsten doped lithium manganese iron phosphate-based fine particle has a composition represented by the following formula (1): LixMn1-y-z-fFeyMzWfPaO4a±p/C (1). In the formula (1), M is Mg, Ca, Sr, Al, Si, Ti, Cr, V, Co, Ni, Zn, or selected from a group consisting of combinations thereof; 0.9≤x≤1.2, 0.1≤y≤0.4, 0≤z≤0.08, 0<f<0.02, 0.1<y+z+f<0.5, 0.85≤a≤1.15, and 0<p<0.1; and the content of C falls in a range of over 0 wt% up to 3.0 wt% to a total weight of the composition represented by the formula (1).SELECTED DRAWING: Figure 1

Description

The present invention relates to tungsten-doped lithium manganese manganese phosphate fine particles, and more specifically to tungsten-doped lithium lithium manganese iron phosphate fine particles for the cathode of a lithium ion battery. The present invention also relates to a tungsten-doped lithium manganese manganese iron phosphate powder material containing the fine particles and a method for producing the powder material.

Lithium-ion batteries are generally used as power storage devices and power supply devices for home appliances, transportation facilities, and the like. Conventional lithium manganese iron phosphate (LMM), which is used as a cathode for lithium-ion batteries, is inferior in electrical conductivity and therefore usually has an electrochemical activity to increase the electrical conductivity. No metal elements are doped.

U.S. Pat. No. 6,514,640

However, the doped lithium manganese phosphate iron usually has a lower electrical capacity than the undoped lithium lithium manganese phosphate iron. Therefore, the energy density of a lithium ion battery made of doped lithium manganese phosphate is very low. Further, the doped lithium manganese phosphate iron usually has a larger specific surface area than the undoped lithium lithium manganese phosphate iron, so that it easily absorbs water. Therefore, the cathode material containing the doped lithium manganese manganese phosphate is difficult to disperse, and the manufacturing cost of the electrode made of the material is high. This is one reason why lithium ion batteries using doped lithium manganese phosphate iron as a cathode material have not yet been widely commercialized.

Therefore, a first object of the present invention is to provide tungsten-doped lithium manganese manganese phosphate-based fine particles for the cathode of a lithium ion battery, which can overcome the above-mentioned drawbacks.

A second object of the present invention is to provide a tungsten-doped lithium manganese manganese phosphate powder material containing tungsten-doped lithium manganese manganese iron phosphate fine particles for the cathode of a lithium ion battery.

A third object of the present invention is to provide a method for producing a tungsten-doped lithium manganese manganese iron phosphate powder material.

In order to achieve the above object, the present invention is a tungsten-doped lithium manganese manganese phosphate fine particle for the cathode of a lithium ion battery, which is a composition represented by the formula (1).
Equation (1) Li _x Mn _{1-y-z-f F y} M _z W _f P _a O _{4a ± p} / C
In the formula (1)
M is selected from the group consisting of Mg, Ca, Sr, Al, Si, Ti, Cr, V, Co, Ni, Zn or a combination thereof.
0.9 ≤ x ≤ 1.2,
0.1 ≤ y ≤ 0.4,
0 ≦ z ≦ 0.08,
0 <f <0.02,
0.1 <y + z + f <0.5,
0.85 ≤ a ≤ 1.15, and
0 <p <0.1,
The amount of C provides tungsten-doped lithium manganese manganese phosphate iron-based fine particles in the range of more than 0 wt% and 3.0 wt% or less based on the total weight of the composition represented by the formula (1). To do.

Further provided is a powder material for a cathode of a lithium ion battery, which comprises the above-mentioned tungsten-doped lithium manganese manganese phosphate fine particles.

Further, (a) in addition to the lithium source, the manganese source, the tungsten source, the iron source, and the phosphorus source, the Mg source, the Ca source, the Sr source, the Al source, the Si source, the Ti source, the Cr source, and V A step of preparing a premix further comprising an additional metal source selected from the group consisting of sources, Co sources, Ni sources, Zn sources or combinations thereof.
(B) A step of adding a carbon source to the premix to form a mixture, and pulverizing and granulating the mixture to form a granular mixture.
(C) Provided is a method for producing the above-mentioned powder material, which comprises a step of subjecting the granular mixture to a sintering treatment to form a tungsten-doped lithium manganese manganese iron phosphate powder material.

Since the powder material containing the tungsten-doped lithium manganese iron phosphate fine particles of the present invention has a relatively small specific surface area, a lithium ion battery manufactured with a cathode material using the powder material is relatively large. It has a discharge specific capacity and a relatively high specific capacity retention rate at a large discharge current.

It is a graph which shows the X-ray diffraction analysis result of the tungsten-doped lithium manganese manganese iron phosphate fine particle of Example 1. It is a graph which shows the charge / discharge specific capacity-voltage relationship of the lithium ion battery of application example 1, comparative application example 1 and comparative application example 2. It is a graph which shows the relationship of the cycle number | discharge specific volume of the lithium ion battery of application example 1, comparative application example 1 and comparative application example 2 at each charge / discharge rate.

The tungsten-doped lithium manganese manganese iron phosphate-based fine particles for the cathode of the lithium ion battery of the present invention are a composition represented by the formula (1).

Equation (1) Li _x Mn _{1-y-z-f F y} M _z W _f P _a O _{4a ± p} / C
In the formula (1), M is selected from the group consisting of Mg, Ca, Sr, Al, Si, Ti, Cr, V, Co, Ni, Zn or a combination thereof.
0.9 ≤ x ≤ 1.2,
0.1 ≤ y ≤ 0.4,
0 ≦ z ≦ 0.08,
0 <f <0.02,
0.1 <y + z + f <0.5,
0.85 ≤ a ≤ 1.15, and
0 <p <0.1,
The amount of C (ie, carbon) is in the range of more than 0 wt% and less than 3.0 wt% based on the total weight of the composition represented by the formula (1).

In certain embodiments, M is Mg (ie, magnesium).

In certain embodiments, f is greater than 0 and less than 0.01 (ie, 0 <f <0.01).

The tungsten-doped lithium manganese manganese iron phosphate powder material for the cathode of the lithium ion battery of the present invention is the powder material containing the above-mentioned tungsten-doped lithium manganese manganese iron phosphate fine particles.

In certain embodiments, the tungsten doped phosphate lithium manganese iron-based powder material ^has a specific surface area in the range of 0.5m ² /g~20.0m 2 / g.

The method for producing a tungsten-doped lithium manganese manganese iron phosphate powder material of the present invention is as follows.
(A) In addition to lithium source, manganese source, tungsten source, iron source and phosphorus source, Mg source, Ca source, Sr source, Al source, Si source, Ti source, Cr source, V source, A step of preparing a premix further comprising an additional metal source selected from the group consisting of Co source, Ni source, Zn source or a combination thereof.
(B) A step of adding a carbon source to the premix to form a mixture, and pulverizing and granulating the mixture to form a granular mixture.
(C) Containing a step of subjecting the granular mixture to a sintering treatment to form a tungsten-doped lithium manganese manganese iron phosphate powder material.

In certain embodiments, tungsten trioxide is used as the tungsten source in step (a).

In certain embodiments, the additional metal source used in step (a) is a magnesium-containing compound (ie, the additional metal is Mg). In the examples shown below, the additional metal source used in step (a) is magnesium oxide.

In a particular embodiment, in step (c), the sintering process is performed at a temperature in the range of 500 ° C. to 950 ° C.

Hereinafter, examples of the present disclosure will be described. It should be understood that these examples are exemplary and descriptive and should not be construed as limiting this disclosure.

Example 1: Production of powder material containing lithium lithium manganese iron phosphate fine particles of _{Li 1.02} Mn _0.72 Fe _0.23 Mg _0.048 W _0.002 PO _{4a ± p} / C ( _{PE1) Shu} Manganese (II) acid (source of manganese (Mn)), iron (II) oxalate (source of iron (Fe)), magnesium oxide (source of magnesium (Mg)), tungsten trioxide (tungsten (W)) ), Phosphorus (source of phosphorus (P)), Mn: Fe: Mg: W: P with a molar ratio of 0.720: 0.230: 0.048: 0.002: 1. At 000, it was added sequentially to the reactor and mixed with water. Then, the mixture was stirred for 1.5 hours and then mixed with lithium hydroxide (a source of lithium, a molar ratio of Li: P of 1.02: 1.00) to obtain a premix.

The premix was then mixed with a combination of citric acid and glucose (carbon source, C: P molar ratio 0.092: 1.00) to give a mixture. The mixture was pulverized for 4 hours using a ball mill, granulated and dried using a spray granulator to obtain a granular mixture.

The granular mixture was sintered in a nitrogen atmosphere at 450 ° C. for 2 hours and then sintered at 750 ° C. for 4 hours to obtain Li _1.02 Mn _0.72 Fe _0.23 Mg _0.048. W was obtained _{0.002 PO 4a ± p / C (} P E1) target powder material comprising tungsten doped lithium manganese phosphate iron-based particles is a _{(P E1).}

The amount of carbon in the tungsten-doped lithium manganese iron phosphate fine particles is 1.53 wt% based on the total weight of the tungsten-doped lithium manganese iron phosphate fine particles.

Comparative Example 1: Production of a powder material containing fine particles of lithium manganese manganese phosphate which is _{Li 1.02} Mn _0.72 Fe _0.23 Mg _0.05 PO ₄ / C ( _{PCE1) The production method of Comparative Example 1 is} , Magnesium oxide, tungsten trioxide and phosphoric acid were added at a molar ratio of Mg: W: P of 0.050: 0: 1.000 (ie, free of tungsten). It is the same as the manufacturing method of.

Comparative Example 2: Production of powder material containing fine particles of lithium manganese manganese phosphate which is _{Li 1.02} Mn _0.72 Fe _0.23 Mg _0.03 W _0.02 PO _{4a ± p} / C ( _{PCE2) Comparison} The production method of Example 2 is that of Example 1 except that magnesium oxide, tungsten trioxide and phosphoric acid were added at a molar ratio of Mg: W: P of 0.030: 0.020: 1.000. It is the same as the manufacturing method.

X-ray diffraction (XRD) analysis:
Powder material of Example 1 _{(P E1)} is, X-rays diffractometer (manufacturer: Bruker, model number: D2 PHASER) were analyzed using. The result is shown in FIG.

As shown in FIG. 1, the tungsten-doped lithium manganese manganese-iron phosphate fine particles contained in the powder material of Example 1 have an olivine-type crystal structure.

Measurement of specific surface area:
Example 1 _{(P E1),} a specific surface area of the powder material of Comparative Example _{1 (P CE1)} and Comparative Example _{2 (P CE2)} has a specific surface area analyzer (manufacturer: Micromeritics, model number: TriStar II3020) using Brunauer -Measured by the Emmet-Teller method (Brunauer-Emmett-Teller measurement, BET, analytical gas: nitrogen). The results are shown in Table 1 below.

As shown in Table 1, since the powder material of Example 1 has a relatively small specific surface area as compared with the powder materials of Comparative Example 1 and Comparative Example 2, it is difficult to absorb water, and the following lithium ion batteries The manufacturing process can be performed more conveniently.

On the other hand, the powder material of Comparative Example 1 in which the lithium lithium manganese iron phosphate fine particles were not tungsten-doped and the powder material of Comparative Example 2 in which the lithium iron manganese iron phosphate fine particles were tungsten-doped in a relatively large amount were It has a relatively large specific surface area and is therefore likely to be seriously affected by the electrolyte solution when lithium ion batteries are manufactured.

Application example 1:
The powder material of Example 1, carbon black and polyvinylidene fluoride (PVDF) were mixed at a weight ratio of 93: 3: 4 to obtain a premix. The premix was mixed with N-methyl-2-pyrrolidone (NMP) to give a paste. Cathode material by applying the paste on aluminum foil to a thickness of 20 μm using the Doctor Blade method and baking at 140 ° C. in vacuum to remove N-methyl-2-pyrrolidone. Got The cathode material was pressed to a thickness of 75 μm using a roller and cut into a circular cathode with a diameter of 12 mm.

Lithium foil was used to create an anode with a diameter of 15 mm and a thickness of 0.2 mm.

Lithium hexafluorophosphate (LiPF ₆ ) is composed of ethylene carbonate (ethylene solvent, EC), ethyl methyl carbonate (ethyl carbonate, EMC) and dimethyl carbonate (dimethyl carbonate, DMC) so as to have a concentration of 1M. (Volume ratio 1: 1: 1) Dissolved in a solvent to obtain an electrolytic solution.

A polypropylene film (polypolylone member, purchased from Asahi Kasei Corporation, 25 μm in thickness) was cut into a circular separator having a diameter of 18 mm. After immersing the circular separator in the electrolytic solution, it was taken out from the electrolytic solution to obtain a dipping separator.

A CR2032 coin-type lithium-ion battery according to Application Example 1 was manufactured by using the above-mentioned cathode, anode and immersion separator together with other parts in an argon gas atmosphere.

Comparative application example 1
The method for manufacturing the CR2032 coin-type lithium-ion battery, which is Comparative Application Example 1, is the same as the manufacturing method for Application Example 1, except that the circular cathode is manufactured using the powder material of Comparative Example 1.

Comparative application example 2
The method for manufacturing the CR2032 coin-type lithium-ion battery according to Comparative Application Example 2 is the same as the manufacturing method for Application Example 1 except that the circular cathode is manufactured using the powder material of Comparative Example 2.

Charge / discharge specific capacity:
The charge / discharge ratio capacity of each lithium ion battery of Application Example 1, Comparative Application Example 1 and Comparative Application Example 2 was measured at a current of 1 C / 0.1 C at 25 ° C. using a battery test device (purchased from MACCOR, USA). Measured at levels and voltages in the range 2.7V to 4.25V. The result is shown in FIG.

As shown in FIG. 2, the lithium ion battery of Application Example 1 had a discharge specific capacity of 144.5 mAh / g. The lithium ion batteries of Comparative Application Example 1 and Comparative Application Example 2 had discharge specific volumes of 141.9 mAh / g and 139.2 mAh / g, respectively. Therefore, the discharge specific capacities of the lithium ion batteries of Comparative Application Example 1 and Comparative Application Example 2 are lower than the discharge specific capacities (144.5 mAh / g) of the lithium ion batteries of Application Example 1.

Cycle charge / discharge measurement Each of the lithium-ion batteries of Application Example 1, Comparative Application Example 1 and Comparative Application Example 2 is in the range of 2.7V to 4.25V using a battery test device (purchased from MACCOR, USA). The measurement was performed by performing three charge / discharge cycles at each current in the order of currents 1C / 0.1C, 1C / 1C, 1C / 5C and 1C / 10C at a voltage and 25 ° C. The result is shown in FIG.

As shown in FIG. 3, the discharge specific capacity retention rate at the discharge current of 10C is the discharge specific capacity of the first charge / discharge cycle of the discharge current of 10C and the discharge of the first charge / discharge sill of the discharge current of 0.1C. Calculated by dividing by the specific capacity.

The discharge specific capacity retention rate of the discharge current of 10C in the lithium ion battery of Application Example 1 was 80.0%. The discharge specific capacity retention rates of the discharge current of 10C in the lithium ion batteries of Comparative Application Example 1 and Comparative Application Example 2 were 65.6% and 77.9%, respectively. Therefore, the discharge specific capacity retention rate of each of the lithium ion batteries of Comparative Application Example 2 and Comparative Application Example 3 is lower than the discharge specific capacity retention rate (80.0%) of Application Example 1.

According to the above contents, the powder material containing the tungsten-doped lithium manganese manganese iron phosphate fine particles of the present disclosure has a relatively small specific surface area. Lithium-ion batteries manufactured using this powder material have a relatively large discharge specific capacity and a relatively high specific capacity retention rate at a large discharge current.

In the above, for illustration purposes, many specific details have been presented to facilitate an overall understanding of the invention. However, it will be apparent to those skilled in the art that one or more other embodiments may be implemented without specific details.

Although preferred embodiments and variations of the present invention have been described above, the present invention is not limited thereto, and all modifications and equivalents are made as various configurations included in the spirit and scope of the broadest interpretation. It shall include the composition.

The tungsten-doped lithium manganese iron phosphate fine particles of the present invention can be applied to the production of cathodes of lithium ion batteries, and lithium has a relatively large discharge specific capacity and a relatively high specific capacity retention rate at a large discharge current. Suitable for manufacturing ion batteries.

Claims (9)

Tungsten-doped lithium manganese manganese phosphate fine particles for the cathode of a lithium ion battery, which is a composition represented by the formula (1).
Equation (1) Li _x Mn _{1-y-z-f F y} M _z W _f P _a O _{4a ± p} / C
In the formula (1)
M is selected from the group consisting of Mg, Ca, Sr, Al, Si, Ti, Cr, V, Co, Ni, Zn or a combination thereof.
0.9 ≤ x ≤ 1.2,
0.1 ≤ y ≤ 0.4,
0 ≦ z ≦ 0.08,
0 <f <0.02,
0.1 <y + z + f <0.5,
0.85 ≤ a ≤ 1.15, and
0 <p <0.1,
The amount of C is tungsten-doped lithium manganese manganese phosphate, which is in the range of more than 0 wt% and 3.0 wt% or less based on the total weight of the composition represented by the formula (1). System fine particles. The tungsten-doped lithium manganese manganese phosphate fine particles according to claim 1, wherein in the formula (1), M is Mg. The tungsten-doped lithium manganese manganese phosphate-based fine particles according to claim 1 or 2, wherein in the formula (1), 0 <f <0.01. Lithium manganese phosphate iron-based powder material for the cathode of lithium-ion batteries
A powder material comprising the tungsten-doped lithium manganese manganese iron phosphate-based fine particles according to any one of claims 1 to 3. Powder material according to claim 4, characterized in that it has a specific surface area in the range of 0.5m ² /g~20.0m ² / g. The method for producing a powder material according to claim 4 or 5.
(A) In addition to lithium source, manganese source, tungsten source, iron source and phosphorus source, Mg source, Ca source, Sr source, Al source, Si source, Ti source, Cr source, V source, A step of preparing a premix further comprising an additional metal source selected from the group consisting of Co source, Ni source, Zn source or a combination thereof.
(B) A step of adding a carbon source to the premix to form a mixture, and pulverizing and granulating the mixture to form a granular mixture.
(C) A method for producing a powder material, which comprises a step of subjecting the granular mixture to a sintering treatment to form a tungsten-doped lithium manganese manganese iron phosphate powder material. The method for producing a powder material according to claim 6, wherein tungsten trioxide is used as the tungsten source in step (a). The method for producing a powder material according to claim 6 or 7, wherein the additional metal source in step (a) is an Mg source. The method for producing a powder material according to any one of claims 6 to 8, wherein in step (c), the sintering treatment is performed at a temperature in the range of 500 ° C. to 950 ° C.

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